Moored (tethered) aerostats have had widespread use in several applications, including surveillance, advertising, and weather monitoring, where the aerostat's stationary position and altitude control allows its objective to be carried out successfully. There has been an increased desire to substitute tethered aerostats or kite-based systems for traditional wind turbines in order to deliver significantly more wind energy than a traditional turbine at a fraction of the cost. In all of these applications, it is desirable that the altitude of the aerostat be controlled and that the aerostat remains steady during operation. For wind energy generation applications, aerostat-based systems offer an advantage over kite-based systems due to the fact that they are based on well-established core technology and include a “lighter-than-air” (often helium) lifting body that provides upward force even in the absence of wind. Still, because such aerostats are often affected by aerodynamic as well as buoyant forces, poor control over attitude can disadvantageously lead to loss of dynamic stability. Furthermore, in applications such as wind energy generation, the performance of the system is contingent not only on altitude control but also on the ability for the aerostat to point in a desirable direction, where the direction that the aerostat points is referred to as its “attitude”.
Prior systems have concentrated on altitude control for tethered aerostats, providing a configuration for which the aerostat remains stationary but is not controlled to a particular attitude. Furthermore, several concepts, such as the method and apparatus described in U.S. Pat. No. 5,080,302, filed Sep. 5, 1990, entitled METHOD AND APPARATUS FOR AERIALLY TRANSPORTING LOADS, by Hoke, provide for this stability by leading the tethers to points on the ground that are widely separated. This type of design requires an elaborate ground station for control of the aerostat altitude and requires an additional pivot at altitude for the aerostat to passively orient itself into the wind, a requirement that is essential for energy generation. Accordingly, there is a need for a system that provides control for a system effectively and efficiently by lessening the need for external control devices and/or sophisticated calibration algorithms, to control attitude of a tethered aerostat.